Radio frequency amplification system



Feb. 25, 1930.

T. F. VOLLTEN 1,748,432

RADIO FREQUENCY AMPLIFICATION SYSTEM Filed Dec. 17, 1923 2 Sheets-Sheet l THEODOEE F VOLLTE N Feb. 25, 1930. T. F. VOLLTEN RADIO FREQUENCY AMPLIFICATION SYSTEM F led De'o. 17, 1923 2 Sheets-Sheet 2 l\ umn nflmmmm Hmuu pgk

N mm a m m F W w M T Patented Feb. 25, 1930 [UNITED STATES PATENT OFFICE THEODORE F, VOLLTEN, BETHESDA, MARYLAND, ASSIGNOR TO PERCIVAL D. LOWELL, OF JAMAICA, NEW YORK RADIO FREGUENCY AI'IPLIFICATON SYSTEM Application filed December 17', 1923. Serial No. 681310.

My invention relates broadly to radio receiving systems, and more particularly to electron tube circuits for amplifyin` incoming` signal energy at radio frequencies, and to a Construction oi' a coupling device tor the efiicient operation of electron tubes in radio frequency amplification circuits.

One of the objects of my invention is to provide a circuit arrangement for an electron tube radio freqneney amplifier which eliminates undesired Oscillations in the electron tube circnits and enables signals or" desired frequency to be received at greater amplitude than heretofore possible.

Another object of my invention is to provide an electrical conpling unit between the several tubes of a radio frequency amplifier with means for' eliminating undesired oscillations which normally cccur in eleetron tube circuits associated with types of coupling units heretofore available.

Still another object of the invention is the provision ot variable means associated with a radio frequency coupling unit for absorb ing undesired oscillatory currents and preventing the transfer of such Currents from one electron tube circut to a succeeding electron tube circuit.

A further object of my invention is to provide a Construction of coupling device for radio frequency amplifiers involving an arrangement of coupling` coils, a va *iable electrical Capacity adapted to tune one of the coils, and a mechanically variable device associated with either of the coils for electrically preventing undesired oscillations in electron tube circuits which may be associated with the coupling coils.

Other and further objects of my invention will be understood from the specification hereinafter following by reference to the accompanyng drawings iorming a part thereof, in which: y

Figure l is a diagrammatic illustration showing the arrangement of my radio frequency amplification system and the mechan- ,ically variable means which I provide for eliminating undesired oscillatory currents from the electron tube crcuits; Fige 2 is a front elex 'ation of mie e, eminent of th conpling device of my invention; Fig. 3 is a si le elevation partially in section llustrating the coupling device shown in illustration in Fig. 2 and showing the variable condenser used for tuning one of the coils of the coupling device mounted concentrically within the coupling coils; Fg. 4 is an elemental diagram representing one arrangement of the coupling coils and the variable means for eliminating nndesired oscillatory currents in electron tube circuits with which the coupling coils may be associated; Fg. 5 is a modified arrangemen of the coupling coils and the mechanically variable means for the suppression of oscillations in circuits connected with the coupling coils; Fig. 6 is a front elevation oi' the elemental arrangement of the parts of the coupling device represented in Fig. 5; Fig. 7 as an elemental diagram of a two-circuit regenerative electron 'tube radio receiver employing the improved coupling device and absorber of nndesired oscillations; Fig. 8 is a diagram showing the application of my coupling device and undesired frequency absorber to a single circuit regenerative radio receiver; and Fig. 9 shows one method which I may em ploy in monnting my coupling device with reference to a variable condenser.

Heretofore in the art radio trequency amplification has been limited in its application by reason of the nndesired oscillatory our rcnts which normally exist between the tube circuits of the amplifier. Several methods have been suggested for reducing these undesired Currents. One method consists in balancing ont the capacities between the several tubes by the proper location of condensers. This method is undesirable due to the fact that it allows a by-pass for radio frequency between the grids of the several tubes, thereby sacrificing a part ot the amplification power of the tubes. In arrangements of this kind each of the tubes are not operated at their point of maximum efi iciency on each of the characteristic curves thereof. It has also been proposed to use a stabilizer connection for placing the proper potential on the grids of the 'tubes of the ainplifier and regulating srch pot tial to a degree where' oseillatons tiizng this sy' the grids are positively biased which so fixes the point on the characteristic curve at which the tube functions that full eflciency for amplification is not obtainable. Radio frequenc transformers heretofore available have been inherently poor in their characteristics properties by reason of the fact that undesired oscillatory currents are transferred from one electron tube circuit to another in the same manner that signal energy of a desired frequency is transferred.

By my invention I provide a radio frequency amplification system in which I absorb undesired oscillatory currents and prevent the transfer thereof from one electron tube circuit to another in the radio frequency amplifier. At the same time, I enable the energy from the output circuit of one tube to be transferred to the input circuit of a succeeding tube of maximum efliciency, in such manner that the tube operates at a point on its characteristic curve with maximum efliciency. The arrangement of my coupling device is such as to absorb undesired oscillatory currents between the tube circuits without detracting from the amplifying qualities of the system. That is to say, where the received sgnalin energy is substantially different in amplitu e than that of the undesired frequencies and the amplifier circuits are tuned to the desired signaling frequency, such desired signaling frequenc will be assed through the am lifier wit out noticea le reduction in amp itude, while undesired frequencies being of smaller amplitude are substantially absorbed. I provide a primary and secondar winding which may have a widely separate ratio. I arrange these windings compactly with relation to each other, either as self-supporting coils or coils located on a substantal insulated support. The coils may be wound adjacent each other or one may be positioned concentrically within the other. A variable condenser may be positioned within the area available within the coils or it may be mounted adjacent the coils to form a compact unit. The undesired frequency absorbing means consists of a conductive rin short circuited upon itself and mounted a jacent one of the coupling coils and mechanically variable in position with respect thereto. This conductive rin is constructed in such manner that its position with respect to the coupling coils may be selected and set. The coupling unit comprsing the pair of coupling coils, the condenser for elec trically tuning one of the coils, and the conductive ring or absorbing undesired oscillatory currents may then be connected between the input and output circuits of a plurality of electron tubes comprisin the radio frequency amplification system. y adjusting the undesired frequency conductive ring I eliminate the undesired frequencies and enable the desired signal frequencies to be efliciently transferred for Operating the tubes at their points of maximum ei`fic1ency.

Referring now more particularly to the drawin s,I have indicated an antenna ground system y reference characters 1 and 2. A coupling device constructed in accordance with my invention is illustrated as included within the dotted lines 3. This device comprises a primary coil 4 and a secondary coil 5. A variable condenser 6 is connected across the secondary coil 5 and forms a part of the coupling unit. The conductive ring 7 for absorbing undesired oscillatory currents is positioned adjacent the seconda coil 5 and is mechanically variable in position with respect thereto. As heretofore stated, the ratio of these windings may be large, the antenna circuit being untuned. I have illustrated the transformer in the diagram as having a step up ratio, that is, the secondary winding has a larger number of turns than the primary winding. I have represented by arrows 8 the fact that the undesired frequency absorber conductive r' 7 is variable in position with respect fo %e coupling coils. The coupling device is connected with the input circuit of electron tube 9 having the usual grid, filament and plate electrodes 10, 11, and 12. The plate circuit of the electron tube 9 is connected to the input of the coupl' device represented as enclosed by dotted lines 14 similar to the coupling device heretofore described. Reference characters 4' and 5' represent primary and secondary windings similar to the windings of the coupling device heretofore described. Reference character' denotes a variable tunin condenser similar to the tuning condenser escribed in connection with the first coupling device, and reference character 7 a denotes an undesired frequency absorbin conductive ring corresponding to the ring described in connection with the first couplng device. Similarly I have represented the parts of coupling devces indicated with dotted lines 15 and 16 by reference characters 4, 5, 6 and 7, and 4, 5, 6, and 7 connected in such manner that tubes 10, 1 7 and 18 function as radio frequency amplifiers. The radio frequency amplifier may employ electron tube detector 19 and two stages of audio frequenc amp1i fication represented at 20 and 21. he loud speaker 22 may be operated from the output of the amplifier and the plate circuits may all be supplied from B battery 23, the filaments of all the tubes being energized from battery 24.

In Figs. 2 and 3 I illustrate one embodiment of my invention in which the primary and secondary windings are mounted ak,- cent each other on a coil support 25. e

coils are spaced apart and a space 26 and 27 thereby provided in which the undesired frequency absorbing ring 7 may be adjusted in position. The variable tunng condenser which is connected across the secondary winding 5, may include rotary plates 28 and stationary plates 29. The rotary plates may be operated from a shaft 30 and control knob 31 from the front of panel 32 on which the coupling device may be mounted.

It will be observed in Fig. 3 that the condenser is mounted concentrically within the coupling coils while in F ig. 9 I show a method of mounting the coupling coils directly upon the rear of the variable condenser fr me represented at 33.

In Fig. l I have illustrated the mechanical adjustments which l may make of the undesired frequency absorbing ring 7 with 'espect to the primary and secondary coils i and 5. As represented by arrows 34 and 35, the ring 7 may be moved into dotted line position 36 or 37 until a position is located at which the undesired oscillations are substantially absorbed and the tubes allowed to operate at their points ot maximum efiiciency. This same adjustment may be obtained in the concentric arrangement ot' coils illustrated in Fig. 5 by arrows 38.

I may also utilize my coupling unit in a two-circuit regenerative receiver illustrated in F ig. 7. In this arrangement a tuned primary 4 and a tuned secondary 5 are cmployed connected to the input circuit of electron tube 39. The undesired frequency absorhing` ring is represented at 7. As represented by arrow 40, the undesired frequency absorhing ring 7 is variable in position with respect to the oscillatory secondary winding 5,

In Fig. 8 I show the application of my coupling device to a single circuit regenerative receiver employing electron tube 4:1 wherein windings 4 and 5 are connected atone end, as indicated at 4:2, and the undesired frequency absorbing ring 7 variably positioned with respect to one of the windings as indicated by arrow 43. It will be understood that the position of the undesired frequently absorbing ring is chosen with respect to the coupling coils so that undesired oscillatory currents are absorbed, annulled and suppressed, enabling the desired signal frequency to be transferred from one electron tube circuit to another with the several tubes operating at points of maximum efiiciency. The coupling coils are designed to efiiciently pass a particular band of frequencies while the conductive ring operates to absorb out of that band the undesired oscillatory frequencies.

The energy absorbing ring is mounted for axial movement with respect to the aXis of the coupling coils, and by moving the ring to a selected position a point is found where undesired oscillatory Currents are eliminated without any considerable reduction in the desired signaling frequency to which the electron tube circuits may be selectively and aecurately tuned.

While I have described my invention in certain particular embodiments, it is to be understood that nodifications may be made and that I intend no limitations upon the inventon other than are imposed by the scope of the appended claims.

What I claim and desire to secure by Letters Patent of the United States is as follows:

l. In a transforming unit for radio amplifiers, tie combination with a pair of aligned transformer *indings in inductive relation to one another, ot a suitable conductor of such area and size as to be capable of preventing tube oscillation disposed in tube oscillation preventing position in the field of the windings and of such low resistance as Compared with that of the windings as to keep resistance less-es at a minimum.

2. In a transforming unit for radio amplifiers, the combination with a pair of transforinei' windings in inductive relation to one another, ot a suitable conductor of such area and size as to be capable of preventing tube oscillation disposed in a position in the field predetermined for the prevention o' self-sustained oscillations in the windings, and oi: such low resistance as Compared with that of the windings as to keep resistance losses at a minimum.

3. In a transtorming unit for radio ampliiiers, the combination with a pair of aligned transformer windings in inductive relation to one another of a suitable conductor adjustably disposed in tube oscillation preventing position in the field of the windings, and a variable condenser disposed adjacent to the windings and adjustable to vary its electrostatic Capacity.

THEODORE F. VOLLTEN. 

